Analysis of Different Strategies for Lowering the Operation Temperature in Existing District Heating Networks

Abstract

District heating systems have an important role in increasing the efficiency of the heating and cooling sector, especially when coupled to combined heat and power plants. However, in the transition towards decarbonization, current systems show some challenges for the integration of Renewable Energy Sources and Waste Heat. In particular, a crucial aspect is represented by the operating temperatures of the network. This paper analyzes two different approaches for the decrease of operation temperatures of existing networks, which are often supplying old buildings with a low degree of insulation. A simulation model was applied to some case studies to evaluate how a low-temperature operation of an existing district heating system performs compared to the standard operation, by considering two different approaches: (1) a different control strategy involving nighttime operation to avoid the morning peak demand; and (2) the partial insulation of the buildings to decrease operation temperatures without the need of modifying the heating system of the users. Different temperatures were considered to evaluate a threshold based on the characteristics of the buildings supplied by the network. The results highlight an interesting potential for optimization of existing systems by tuning the control strategies and performing some energy efficiency operation. The network temperature can be decreased with a continuous operation of the system, or with energy efficiency intervention in buildings, and distributed heat pumps used as integration could provide significant advantages. Each solution has its own limitations and critical parameters, which are discussed in detail.

Reduction of Heat Losses in a Pre-Insulated Network Located in Central Poland by Lowering the Operating Temperature of the Water and the Use of Egg-shaped Thermal Insulation: A Case Study

“…[1] showed that the construction of a network in urban areas causes a significant reduction of carbon dioxide emissions to the air, while Ravina et al [2] pointed out that district heating networks could contribute to the reduction of emissions of nitrogen oxides and suspended particulates in the Italian city of Turin. The ecological effect may be raised by the cooperation of district heating networks pre-insulated especially by low-temperature heating networks with renewable heat sources [3,4]. The work of district heating networks is undoubtedly influenced by the management of district heating networks [5][6][7], as well as the type of local heat consumers [7,8].…”

Energy, Environmental, and Economic Analyses of a District Heating (DH) Network from Both Thermal Plant and End-Users’ Prospective: An Italian Case Study

“…The results obtained with the DH network were (i) energy savings higher than 21% for 33% of the campus buildings, (ii) increase in consumption of 20% in 17% of the buildings, and (iii) no significant differences in the remaining buildings. Neirotti et al [20] studied two different approaches for decreasing the DH operating temperatures, starting from a different control strategy involving night-time operation to avoid the morning peak demand, and the partial insulation of the buildings to decrease the operating temperatures without modifying the heating system of the end-users. In the first approach, it was possible to decrease the network temperature down to 50-60 • C without compromising the comfort and the end-users' energy consumption increased by 3.5% with respect to the reference case due to the continuous operation of the heating system, although the network losses decreased.…”

Dynamic Approach to Evaluate the Effect of Reducing District Heating Temperature on Indoor Thermal Comfort

“…However, when the user system is separated from DH network by a heat exchanger (indirect connection), the actual radiator supply temperature strongly depends on the type of control and on the characteristics of the heat exchanger. Neirotti et al [31] explore the effect of reducing DH temperature on a typical North-Italian building with radiator-based heating, comparing two different refurbishing strategies based on continuous operation and on building insulation improvement. They assume a coil heat exchanger modeled by means of a Modelica library component, although DH substations more often use plate heat exchangers.…”